1. Field of the Invention
The present invention relates to a mower which includes a cutting mechanism which during operation extends transversely to the direction of operation; an attachment structure which is to be connected to a motorized vehicle; and a carrying beam connected on one hand to the cutting mechanism by means of a first articulation with an axis directed forward, and on the other hand to the attachment structure by means of a second articulation with an axis directed forward and by means of a third articulation with an axis directed upward, which allows pivoting of the second articulation with respect to the attachment structure.
The mower of the present invention further includes a safety device which holds the cutting mechanism in normal operating position, but allows it to pivot rearwardly about the axis of the third articulation in case an obstacle is encountered, said safety device including an energy accumulator.
2. Discussion of the Background
Such a mower is described in document FR-A-2,384,431. The safety device of this mower includes a traction spring. The spring is connected at one of its ends to the cutting mechanism in the vicinity of the first articulation, connecting the cutting mechanism to the carrying beam. At its other end, the traction spring is connected to a support fixed to the attachment structure. Bars, which are parallel to the traction spring, limit the elongation of the traction spring.
During normal operation, the cutting mechanism, which is in contact with the ground, follows the relief of the terrain by means of the first articulation which connects the cutting mechanism to the carrying beam, and by means of the second articulation which connects the carrying beam to the attachment structure. Considering the arrangement of the traction spring, a large part of the weight of the cutting mechanism is transferred to the attachment structure and at last to the tractor to which the attachment structure is connected. In this manner, the cutting mechanism rests only with slight pressure on the ground as is perfectly known in the art of mowing machines. The traction spring thus performs a primary function of lightening the cutting mechanism.
When the cutting mechanism strikes an obstacle found in the field, it pivots together with the carrying beam toward the rear about the axis of the third articulation which connects the second articulation to the attachment structure. While accomplishing this, the cutting mechanism tightens the traction spring which has the effect of further lightening the cutting mechanism, even simply lifting it, thereby facilitating its passage over the obstacle. When the obstacle no longer acts on the cutting mechanism, the traction spring brings the cutting mechanism and the carrying beam back to normal operation position. The same traction spring thus carries out a second function of safety in case of striking an obstacle, thereby protecting the mower.
This safety device offers the important advantage of resetting itself automatically as soon as the obstacle is cleared and/or no longer acts on the cutting mechanism, contrary to other existing safety devices which require a series of steps to be reset if they become disengaged.
This safety device, however, has the disadvantage of being very sensitive to the configuration of the ground. Indeed the terrain areas to be mowed are not entirely flat surfaces, but have a large number of more or less large bumps. The safety device reacts to almost every one of these bumps, which in turn almost constantly cause small pivotal movements of the cutting mechanism and the carrying beam about the axis of the third articulation. This continual working is harmful to the quality of cutting and causes vibrations which are harmful to the operational durability of the mower and are very annoying to the driver because they are transmitted to the tractor via the attachment structure.
Another disadvantage of this safety device lies in the fact that at the time an obstacle is encountered, the stresses caused in the different elements of the mower increase in proportion to the angle of pivoting of the cutting mechanism.